Variability across Climate Model Simulations of future wind regimes in West Africa

Abstract

Reliable wind assessments are essential for energy planning in West Africa, where demand is increasing and decarbonisation targets are becoming more stringent. The purpose of this study is to evaluate both the credibility and the variability of global climate models simulations for wind regimes in West Africa dividided into five sub-regions (Atlantic coastal, southern coastal, sub-Saharan, Sahel, and Sahara), using ERA5 reanalysis as a benchmark for evaluating model performance as well as projecting future regimes under climate scenarios for better energy planning and relevance policy informed decision making. First, the past-to present climatological analysis with the ERA5 wind speed data for the period 1950-2024 show that the Atlantic coastal region and the Saharan have strongest and moderate mean wind speed respectively above 3 m/s or around. While most of the Sahelian, sub-Saharan and southern coastal regions show low mean wind speeds between 1-3 m/s. Secondly the long-term wind speed anomalies shows positive and negative values, with |anomaly| ≥ 0.2 m/s across all subregions, except the sub-Saharan region where anomalies fall below 0.2 m/s in absolute value. Futhermore, findings present a relatively low or almost no trend over the study period. The resuluts of seasonal variability and extremes events across the sub-regions show that high wind speeds occur in DJF, MAM for the Atlantic coastal region, in JJA for Southern Coastal and sub-Subsahara, in DJF for Sahelian and Sahara. Four CMIP6 models (MIROC6, HadGEM3-GC3, CESM2-WACCM, MPI-ESM1-2HR) were used for historical wind speed projections.The historical projections show a robust coastal-inland gradient across models with observed individual biaises: the highest mean winds are found on the Atlantic coast and the Saharan fringe, the lowest in the sub-Saharan belt and variability increases inland. The models were compared to ERA5 and the statistically best performing model MPI-ESM1-2LR (mean bias = +0.07m/s, MAE = 0.41m/s; RMSE = 0.52m/s, r = 0.90; R² = 0.78 ) was used for the 2025-2075 projections under SSP2-4.5 and SSP5-8.5 considering DJF and JJA seasons. The future projections conserve the historical gradient but present a generalised weakening inland, weaker and more irregular in the SSP2-4.5 scenario and more widespread in the SSP5-8.5 scenario, particularly during the JJA period in the southern coastal, sub-Saharan and Sahelian areas; the Atlantic coastal corridor remains relatively robust, while the Sahara shows mixed seasonal changes. These results imply that for better regional energy planning we should prioritise grid-connected coastal and offshore projects, combine wind energy from the south coast with photovoltaic energy and storage to address seasonal variability, adopt hybrid strategies and targeted micro-deployment inland, and take into account transport and maintenance constraints for Saharan options